The B1855 Diagnostic Trouble Code (DTC) indicates a problem with the internal air temperature sensor motor circuit in a vehicle's climate control system. This issue, a short to battery, can disrupt the system's ability to accurately monitor and regulate the cabin temperature, leading to discomfort and potential malfunctions. Addressing this promptly ensures optimal climate control performance and prevents further damage to the system.
| Topic | Description | Possible Causes |
|---|---|---|
| Definition of B1855 | Diagnostic Trouble Code indicating a short to battery in the internal air temperature sensor motor circuit. | Wiring issues, faulty sensor motor, damaged climate control module. |
| Symptoms | Incorrect cabin temperature, climate control system malfunctions, blower motor issues, error codes on the display. | Inaccurate temperature readings, erratic climate control behavior, system shutdown. |
| Internal Air Temperature Sensor Motor Function | Controls the movement of a damper or vane that directs airflow over the internal temperature sensor. This ensures accurate temperature readings. | Optimizes sensor performance by ensuring consistent airflow. |
| Common Causes of the Short | Damaged wiring insulation, corrosion in connectors, internal short within the sensor motor, faulty climate control module. | Abrasion, environmental exposure, component failure. |
| Diagnostic Steps | Visual inspection of wiring and connectors, testing sensor motor resistance and voltage, checking for power shorts to ground, diagnosing the climate control module. | Systematic elimination of potential causes. |
| Tools Required for Diagnosis | Multimeter, wiring diagrams, scan tool, basic hand tools. | Accurate electrical measurements and system information. |
| Potential Fixes | Repairing or replacing damaged wiring, cleaning or replacing corroded connectors, replacing the internal air temperature sensor motor, replacing the climate control module. | Restoring proper circuit function. |
| Impact on Climate Control System | Inaccurate temperature regulation, inefficient heating and cooling, potential system failure. | Compromised comfort and performance. |
| Related Diagnostic Trouble Codes | Other climate control system codes related to sensor malfunctions or circuit issues. | B1856, B1857, B1858, etc. |
| Importance of Addressing the Issue | Ensures proper climate control function, prevents further damage to the system, maintains driver and passenger comfort. | Long-term system reliability and comfort. |
Detailed Explanations
Definition of B1855: The B1855 DTC signifies that the vehicle's computer has detected an unwanted electrical connection between the internal air temperature sensor motor circuit and a power source (battery voltage). This short circuit can disrupt the normal operation of the climate control system.
Symptoms: When the B1855 code is present, drivers might experience several symptoms. These include an inability to accurately control cabin temperature, the climate control system malfunctioning entirely, issues with the blower motor's operation, and visible error codes displayed on the vehicle's information system. The system may blow hot air when cold is desired, or vice versa.
Internal Air Temperature Sensor Motor Function: The internal air temperature sensor motor plays a crucial role in the climate control system. It controls the position of a small damper or vane that directs airflow over the internal temperature sensor. This ensures that the sensor receives a consistent and accurate reading of the cabin's air temperature, which is then used to regulate the heating and cooling systems.
Common Causes of the Short: Several factors can lead to a short circuit in the internal air temperature sensor motor circuit. These include damaged wiring insulation (caused by abrasion or heat), corrosion within electrical connectors, an internal short within the sensor motor itself, or a failure within the climate control module that controls the system. Rodent damage can also be a culprit.
Diagnostic Steps: Diagnosing the B1855 code requires a systematic approach. This typically begins with a visual inspection of the wiring and connectors associated with the internal air temperature sensor motor. Next, the sensor motor's resistance and voltage are tested using a multimeter. The technician will also check for power shorts to ground and, if necessary, diagnose the climate control module itself. A scan tool is used to read the code and monitor sensor data.
Tools Required for Diagnosis: A variety of tools are needed to properly diagnose the B1855 code. These include a multimeter for measuring voltage, resistance, and continuity; wiring diagrams specific to the vehicle model; a scan tool to read and clear diagnostic trouble codes; and basic hand tools for accessing components and connectors. A smoke machine may be used to check for leaks in the ductwork.
Potential Fixes: The appropriate fix for the B1855 code depends on the underlying cause of the short circuit. Potential solutions include repairing or replacing damaged wiring, cleaning or replacing corroded connectors, replacing the faulty internal air temperature sensor motor, or replacing the climate control module if it is determined to be the source of the problem.
Impact on Climate Control System: The B1855 code directly impacts the climate control system's ability to regulate temperature accurately. This can lead to inefficient heating and cooling, compromised passenger comfort, and, in severe cases, a complete failure of the climate control system. The system may overwork itself, leading to premature wear and tear on other components.
Related Diagnostic Trouble Codes: Other DTCs related to the climate control system can sometimes accompany the B1855 code. These might include codes indicating other sensor malfunctions or circuit issues within the system, such as codes for the external temperature sensor or the blend door actuator. Common examples include B1856, B1857, and B1858, which may indicate problems with other components in the HVAC system.
Importance of Addressing the Issue: Addressing the B1855 code is crucial for ensuring the proper function of the climate control system. This ensures optimal temperature regulation, prevents further damage to the system's components, and maintains driver and passenger comfort. Ignoring the problem can lead to increased repair costs down the line.
Frequently Asked Questions
What does the B1855 code mean? The B1855 code indicates a short to battery in the internal air temperature sensor motor circuit. This means there's an unintended electrical connection causing the motor to receive excessive voltage.
Can I drive with a B1855 code? While you can technically drive with a B1855 code, it's not recommended. The climate control system may not function properly, leading to discomfort, and the underlying issue could potentially damage other components.
How do I fix a B1855 code? Fixing a B1855 code involves diagnosing the cause of the short circuit and addressing it. This may involve repairing or replacing damaged wiring, cleaning corroded connectors, or replacing the sensor motor or climate control module.
Is the internal air temperature sensor the same as the ambient temperature sensor? No, the internal air temperature sensor measures the air temperature inside the cabin, while the ambient temperature sensor measures the air temperature outside the vehicle. They serve different purposes in the climate control system.
Will replacing the sensor always fix the B1855 code? Not necessarily. While a faulty sensor motor can cause the B1855 code, the problem could also be due to wiring issues, connector corrosion, or a faulty climate control module. Thorough diagnosis is crucial.
Conclusion
The B1855 Diagnostic Trouble Code signifies a significant issue within the vehicle's climate control system, specifically a short to battery in the internal air temperature sensor motor circuit. Proper diagnosis and repair are essential to restore the system's functionality, ensure passenger comfort, and prevent further damage. Consulting a qualified automotive technician is recommended if you lack the necessary tools and expertise.